The most important discovery in human historyLies beneath our feetHidden by the secrets of the surface worldThis sourcebook expands Hollow Earth Expedition to include the mysterious and perilous surface world, filled with dangerous criminals, mad scientists, and dark sorcerers! Become a daredevil pilot, private detective, or wandering hero, exploring exotic locales and thwarting evil plots. Meanwhile, world powers and secret societies vie for control of what may be the most important discovery in all of human history: the Hollow Earth!Inside you will find everything you need to run thrilling surface world adventures or add more spice to your existing Hollow Earth games: new rules for psychic powers, sorcery, and weird science; an expanded vehicle and equipment catalog; and additional details on secret societies and surface world locations.